A group of disaffected priests inside the Vatican claimed yesterday that the commander of the Swiss Guard who was murdered last year was the victim of a Vatican power struggle.

The authors, identified anonymously as "the disciples of truth", claim that evidence was tampered with in order to fit the hypothesis that the killing was the result of a moment of madness on the part of a non-commissioned officer, Cedric Tornay. The claim, printed by a small Milan publisher in a book entitled Blood Lies in the Vatican, is the latest scandal to rock the Catholic church.

Coming only a day after the decision by prosecutors in southern Italy to recommend that the cardinal of Naples be sent for trial on charges of loan-sharking, the latest allegations are causing acute unease throughout the clerical hierarchy.

Emotionally unstable and convinced that he was being victimised by Colonel Alois Estermann, according to the Vatican account, vice-corporal Tornay shot dead his newly appointed commander and Estermann's Venezuelan wife, Gladys Meza Romero, before turning his revolver on himself.

But according to the anonymous authors, Col Estermann was the victim of a struggle for control of the Swiss Guard - which had been in charge of papal security for the past five centuries - between the secretive, traditionalist Catholic movement Opus Dei and a masonic power faction ensconced in the Curia.

"In the Vatican, there are those who maintain that vice-corporal Tornay was attacked after coming off duty and dragged into a cellar," the book says. Tornay was then "suicided" with a silenced 7mm pistol, and his duty revolver used to kill the Estermanns in their Vatican apartment. His body was dumped in the Estermann's flat so that the triple killing would look like a murder-suicide.

"It is murmured that Alois and Gladys Estermann and Cedric Tornay were killed by a commando [unit] comprising a killer and two accomplices. It is said that someone saw the commando but will never testify to that effect," the authors say.

The authors, who appear to have had a detailed knowledge of many of the episodes they describe, alleged that four used glasses, originally present in the flat, subsequently disappeared, along with the photographs taken by the first official photographer to arrive on the scene.

Both Col Estermann and his wife, who worked at the Venezuelan embassy to the Holy See, were actively engaged in secret international financial deals for the benefit of Opus Dei, the book alleges.

Opposition to Col Estermann's appointment resulted in a nine-month power vacuum at the head of the guard. Just nine hours after the announcement of the Vatican's choice, the new commander was dead.

"Before the arrival of the magistrate, someone searched not only the Estermann's apartment, but also the commander's office and the vice-corporal's room in the barracks," it alleges.

"The element that undermines the official truth is the fact that no one heard the five loud shots fired, according to the Holy See, by the powerful pistol found under Cedric Tornay's body."

Superficial investigation

The book argues that the Vatican's investigation was superficial and tailored to coincide with the reconstruction offered immediately after the event by the Vatican spokesman, Joaquin Navarro Valls, himself a member of Opus Dei.

It contains a footnote written by Tornay's mother, Muguette Baudat, expressing her dissatisfaction with the way the Vatican handled the affair.

"Reasons of state appear to reign at the head of the church, and I think this is the origin of the great effort made by the heads of the Roman Curia to prevent a terrible truth being revealed to the world," Ms Baudat writes.

Blood Lies in the Vatican also examines financial scandals that have tarnished the Vatican's reputation in the past.

It claims that in 1982 the Banco Ambrosiano affair, which at one point resulted in magistrates issuing an arrest warrant for Archbishop Paul Marcinkus, the head of the Vatican bank, was part of the same power struggle between freemasons and Opus Dei that cost Col Estermann his life almost two decades later.

If anything, the request that Cardinal Michele Giordano of Naples be tried for usury is even graver than the scandal that lapped around Archbishop Marcinkus's institute for the works of religion.

As church head in a major Italian city, the short, portly Cardinal Giordano is an authentic prince of the church and it is unprecedented for the Italian judiciary to move against a figure of such seniority. The crimes of which he is accused - usury, criminal conspiracy and embezzlement - have a particular social gravity in Italy's impoverished south.

Yesterday, the Vatican maintained silence on his case and Vatican radio and the semi-official newspaper Osservatore Romano pretended it had never happened. But other Catholic newspapers and his supporters said he was a victim of a vendetta by leftwing prosecutors.